UNIX Programming Final REview

Command line utility for compiling large programs

make -f <makefileName> target

target: sources
\t command

KEYWORD = contents

$(KEYWORD)

A make target that does not generate any files

Target name

All sources

Left-most source

A sequence of instructions executed independently of a parent process. Can be run in parallel.

Process ID, Address Space (Code + Data + Memory), File Descriptors, Working Directory, User/Group ID

Thread ID, Registers, Stack

-pthread

<pthread.h>

int pthread_create(pthread_t* thread, const pthread_attr-t* attr, void* (*startroutine)(void*), void* arg)

int pthread_exit(void *value_ptr)

int pthread_join(pthread_t thread, void **value_ptr)

void* func(void* args)

A lock for making sure there are no data races between threads. A thread can lock a mutex if it's unlocked, otherwise it has to wait until it's unlocked. Has type pthread_mutex_t.

pthread_mutex_init(&mylock, NULL)

pthread_mutex_lock(&mylock)

pthread_mutex_unlock(&mylock)

Physical, Data Link, Network, Transport, Session, Presentation, Application

Sendecieve bits over a medium (wire/air)

Multiple computers on a LAN. Specifies how bits are peketized. Uses Media access control (MAC) and network interface controllers (NICs).

Routes information between various networks by IP address. Defines a protocol to route packets.

Provides an end-to-end direct connection, abstracting away connection details. Provides different protocols (like TCP and UDP) to interface between source and destination.

Transmission control protocol. Provides applications with reliable, ordered byte streams. Sends stream data as multiple IP packets and retransmits them as necessary. When receiving, puts packets back in order and detects missing packets. A single host (IP address) can have up to 2^1 = 65535 ports.

Provides applications with unreliable packet delivery. A thin, simple layer on top of IP, with data still fragmented into multiple IP packets.

Session - Supposedly handles establishing and terminating application sessions
Presentation - Fragments data into multiple IP packets (???, the slides are unclear and it sounds like it's doing the work of the network protocol)

Defines a protocol for the format and meaning of messages between application entities, like HTTP or your favorite multiplayer video game.

Application -> Physical

Physical -> Application

A file descriptor for network communications.

Stream, Datagram, Raw

For connection-oriented, point-to-point, reliable byte streams. Uses TCP, SCTP, or other stream transports.
Establish connection -> Communicate -> Close connection

For connection-less, one to many, unreliable packets. Uses UDP or other packet transports
Create Sockets -> Communicate

For layer-3 communication (raw IP packet manipulation)

Step 1: Figure out the IP Address and Port. You may need to obtain the IP Address from the DNS via getaddrinfo(const char* hostname, const char* service, const struct addrinfo* hints, struct addrinfo** res).
Step 2: Create a socket using socket(int domain, int type, int protocol). This returns a socket file descriptor.
Step 3: Connect to a server using connect(int sockfd, const struct sockaddr* addr, socklen_t addrlen).
Step 4: Use read and write to communicate over the file descriptor.
Step 5: Use close(sockfd) to close the connection.

Step 1: Figure out the IP address and port on which to listen. Again may need to use getaddrinfo(const char* hostname, const char* service, const struct addrinfo* hints, struct addrinfo** res).
Step 2: Create a socket using socket(int domain, int type, int protocol). This returns a socket file descriptor.
Step 3: Bind the socket using bind(int sockfd, constr struct sockaddr* addr, socklen_t addrlen).
Step 4: Create a listening socket that clients can connect to using listen(int sockfd, int backlog).
Step 5: Accept an incoming client connection using accept(int sockfd, struct sockaddr* addr, socklen_t* addrlen).
Step 6: Use read and write to communicate over the file descriptor.
Step 7: Use close(sockfd) to close the connection.

A program that lets a user or other program use an operating system's services or programs.

A shell program

var=contents
echo $var echo "$var"

get_name() {
echo "John"
}

echo "You are $(get_name)"

echo "I'm in $(pwd)"

if [[ -z "$string" ]]; then echo "String is empty" elif [[ -n "$string" ]]; then
echo "String is not empty"
fi

echo $((2+3))

A sequence of characters that can match a pattern.

Sequence: ab
Range: [a-z]
Alternation apple|cherry
Repetition: a{2,3}, a*, a+, a?
Group: (ab)
Beginning/End: ^, $ Match any character: . Match any word character: \w

A datacenter hardware and software that are used to offer computing resources and services

Public Cloud - Available to the public, pay-as-you-go, service sold is utility computing
Private Cloud - Internal data-centers of organizations not available tothe public, managed internally or by third-party providers, involved CapEx
Hybrid Cloud

Infrastructure-as-a-service - Basic computing resources, users control the software stack from the kernel upward, provider cannot offer scalability and fail over
Server-less - Application domain specific platform (AppEngine), request-reply based, automatic scaling, not suitable for general purpose computing
Platform-as-a-service - Supports general purpose computing, users can choose language but not libraries, OS, automatic scaling but requires configuration by users